In the present specification the spatial configuration of the substituents related to the chiral carbon atom denoted with ".alpha." is characterized by "S" and "R", respectively. The designations "cis" and "trans", respectively, mark the position of the substituents attached to carbon atom "3" of the cyclopropane ring related to the spatial configuration of the substituents of carbon atom "1". The absolute spatial configuraton of the substituent attached to carbon atom "1" is denoted with the prefix "1R" and "1S", respectively.
In the present specification the various enantiomers and enantiomer-pairs are designated with the following abbreviations:
Ia: mixture of 1RcisS and 1ScisR PA1 Ib: mixture of 1RtransS and 1StransR PA1 Ic: mixture of 1RcisR and 1ScisS PA1 Id: mixture of 1RtransR and 1StransS PA1 If: 1RcisS PA1 Ig: 1RtransS PA1 Ih: 1ScisR PA1 Ii: 1StransR PA1 lower toxicity on warm-blooded species and humans; PA1 more economical manufacturing process; PA1 smaller damages caused to useful parasites and bees.
It is known that pyrethroids of the Formula /I/ (known under the generic name "cypermethrin") belong to the valuable family of synthetic pyrethroids and are useful as insecticide (Hungarian Pat. No. 170,866). These compounds may be prepared by reacting m-phenoxy-benzaldehyde cyanohydrine with the corresponding cyclopropane carboxylic acid chloride in the presence of a base [Pestic. Sci. 6, 537, . . . 1975]. The product thus obtained consists of eight stereoisomers i.e. of a mixture of four enantiomer-pairs. If a 60:40 mixture of the corresponding trans and cis cyclopropane carboxylic acid chlorides is used, the mixture contains 18-19% of enantiomer-pair Ia, 21-22% of enantiomer-pair Ic, 26-27% of enantiomer-pair Ib and 33-34% of enantiomer-pair Id.
According to prior art the steroisomers of cypermethrin show different biological activity. It is generally accepted that the activity of molecules comprising cis cyclopropane carboxylic acids is superior to that of the corresponding trans derivatives [Pest. Sci. 7, 273, 1976].
In the comparative biological tests of various pyrethroids [Pest. Sci. 9, 112-116 1978] the cis and trans stereoisomers--including the cypermethrin stereoisomer-pairs--were evaluated together.
The comparative tests were carried out on Musca domestica L. and Phaedon cochleariae Fab species. Concerning the chloro derivatives from the trans isoomers activity data of 1RtransS Ig and 1RtransR were disclosed. The said data show that--while the 1RtransS isomer possesses a strong activity--the 1RtransR isomer is considerably less active [according to the test the activity related to bioresmetrine 100 amounts to 1400 and 81, respectively, on Musca domestica and to 2200 and 110, respectively, on Phaedon cochleariae]. It was disclosed further that the activity of a mixture of both tested isomers was lower than the calculated value. Thus the isomers showed an antagonism rather than the expected synergism and the rate of antagonism amounted to 1.42 and 1.46 on house fly and mustard beetle, respectively.
As a result of the said test and publications the trans isomers and mixtures thereof were pushed to the background of biological interest and research was focused to active cis derivatives and mixtures thereof. This lead to the development of alphamethrin (isomer mixture of 1RcisS and 1ScisR Ia) of the chloro derivatives) and decamethrin [comprising the 1RcisS isomer (If) of the bromo derivatives].
Similar data were set forth for the bromo derivative; on mustard beetle the rate of antagonism amounts to 1.48.